For the given WebAudio AnalyserNode, determine the average signal (0 .. 1) between two frequency ranges in Hz. This can be useful for audio visualization on a certain spectrum of the frequency graph.
The frequency is assumed to be in byte data, though you can use the floatData entry point to get around this.
Returns the average signal in 0 .. 1 range for the given analyser (AnalyserNode) and frequencies (array of byte frequency data from that node). The minHz and maxHz is the frequency range to sum, in Herz.
The same as above, but intended to be used with the result of analyserNode.getFloatFrequencyData().
MIT, see LICENSE.md for details.